Soaking pit



Sept. 23, 1 952 MOWAT 2,6` ,6oo

SOAKING ?IT Filed June l, 1948 2 SHEETS--SHEET 1 31 22 28 31 12 :z 10 f I INVENTOR. JOHN F MowAT ATTORN EY Patented Sept. 23, 1952 UNITED gsTATEs PArNT O FICE John F. Mowat, La Grange, Ill., assignor to v t United States Steel Company, a corporation of New Jersey ApplicationJune 1 1948, Serial No. 30,256

This invention relates to apparatus for heating ingotsand, in particular, to a soaking pit having a separate combustion chamber and connections for conducting combustion gases from the chamber; to the pit.

Although soaking pits have known to me have burners firing directly thereinto.

the ingots. This causes "washing'f or local overheating' and melting of the ingots as well as been improved in' e many -respects in recent years. all modern pits y Considerable dirculty is still experienced, therefore, as a result of name impingement on V excessive oxidation thereof, both of which impair the 'quality of the product. Fuel consumption remains high, urthermore, despite the general It is accordingly the object j` use of recuperators. o my invention to provide a soaking pit constructed to heat ingots solely by contact of hot combustion gases withoutdirect fiame impingement and to reduce the uel Consumption.

In a preferred embodiment and practice, I provide a combustion chamber adjacent the pit and effect'substantially complete burning of the fuel inlet ports' spaced around the top thereoi. After passing' downwardly over the ingots;` 'the therein. combustion gases 'are led from the chamber and introduced 'into the pit through gases 'are exhausted through out1et'por`ts spaced j around the bottom of the pit. This causes the pit to be filled with gas at substantially uniform temperature and pressure.: The inlet and outlet ports communicate, respectively, with supply and exhaust flues extending around the pit. The combustion chamber islocated at one side of,

the pit and isconnected directly to the supplyflue. Air for combustion is heated by recuperators in the stack fiue connection. I also provide a beat-exchange wall for the combustion cham-- ber -and cause the entering air to pass through it to cool the wall and heatthe air further.

A complete understanding of -the invention may be obtained from the following detailed de-` scription and explanation which refer to the accompanying drawings illustrating a present preferred .embodiment. In the drawings,

Figure 1 is a central longitudinal vertical section through the soaking pit of my inventioni andthe' associated combustion chamber;

Figures 2 through 4 are transverse sections to a. reduced scale taken along the planes of lines II-II, III-III and IV-IV, respectively, of Figure 1;

Figure 5 is a horizontal section taken along the plane of line V-V of Figure 1; and

-Figure 6 is a plan view cover removed.

of the pit with the 5 Claims. (01.263-20) Referring in detail to the drawings, the apparatus of my invention comprises a soaking pit o and a combustion chamber 'l xtending across one side thereof. The drawings show only the walls of the chamber and pit, the structural binding thereof being omitted as `well as dampers or other flow-control means. As shown in Figures 5 and 6, the pit is rectangular in plan, being de fined by side walls 12-, and is open at the top, being provided with a cover !3 removably disposed thereover; The usual sand seal 13 extends around the top of the'pit. The walls of the pit and combustion chamber are constructed in the known manner by 'laying up brick of suitable composition and characteristics on a foundation ll, the pit, combustion chamber and hot-gas flues connected therewith, as will be described in detail later, being lined with refractory brick. The bottom of the pit, indicated at 15, comprises a refractory hearth laid on supporting beams !6 and provided with a-layer of coke breeze in which the ingots to be heated are stood on end.

-As shown in Figures 1 and 5, the combustion chamber H has a length and height somewhat greater :than the corresponding dimensions of the pit Io. The length and height of the chamber ll-, fu'rthermore, are several times the width thereof. The chamber is divided by wall I'I into forth-and-return passes l8 and !9 connected by a port 211. 'The wall l'l is hollow and is provided with vertically spaced baffies 2! defining a continuous passage therethrough for a purpose which will appear shortly. The pass IS is provided with'a bame 22 and the pass [9 with bafiies 23 which cause turbulence in the combustion gases flowing therethrough and 'also brace and stay the walls of the combustion chamber.

Burners 24-fire into the pass !8 of the combustion chamber,- being supplied with any desired type of fuel from a suitable source through a connection 25. This connection extends through an air chamber 26 which receives air preheated for: combustion, through a downcomer duct 21 from* a source which will be described later. The supply of fuel and air to the burners 24 is preferably controlled so that combustion of the fuel is' substantially completed' before the burning gases pass upwardly over' the bafiie 22. After passing the bame, the gases flow downwardly, through port 20 and thence back through the return pass !9 around the battles 23.

-A fiue 28 for supplying hot gases to the pit ID extends about the latter at a level somewhat be low the top, the flue being rounded at the corners, as indicated at 28 to facilitate smooth flow of the gases therethrough. A port 29 extends from tributed substantially uniformly along the four,

sides of the pit, each side having a multiplicity of passages therein, as shown.

By virtue of the Construction described, na combustion gases flowing V 'from ;chamber l l through the passage 29 into the fiue' 28 pass 'upwa-rdly through the passages 3 I, strike the bottom of the cover s and are thereby deflected `downwardly into the pit. The ue 28 being continuous, any portion of the gases fiowing therethrough which does not pass upwardly through the passages 3! is recirculated on returning to the inter-section of the passage 29`with the fl'ue where the 'recirculating gases mingle with the fresh combustion gases ente-ring from the chamber H. There will naturallybe a-slight fall in gas-pressure from'the passage 29 around` the'flue !Bin the direction' of flow ofgases. In' order to tnsure substantially uniform flow of hot gases upwardly` through passages=3| and downwardly over the rim of the pit at all points along the periphery thereof, l employ dampers in` the form of refracto-ry tiIe-s' 32. These dampers are adjusted manually to overlie the ports 3| at the upper ends of the passages 3l, to the extent necessary to maintain the desired uniform distributi'on of 'inrlowi'ng hot gases despite the fact that the' pressure thereof diminishes gradually as they travel around the ue 28. e An' exhaust flue 33 extends around the pit o at a level adjacent the bottom thereof and passages 34 extend thei-eto from-'outletports 3 spaced along theside' wall's z, 'The hot gases enter-ing the top of the pit thus flow downwardly over theingots standing therein,as indicated at 35, 'and thence outwardly through the -passages Stand 'flue-33-. Astack flue 36 extends transversely of the pit below the bo-ttom'thereof and hasan inclu'ced draftfan 31 th'ereih on the burner side." A reeuperator chamber 38 is formedbetween the flue 33 and-the flue 35 and is provided with heat'exchangers ils in the form. of banks of ahtubes. V `Air for'combustion in' the chamber ll is supplied by' a forced draft fan 40, the outlet of which is connected to a duet 4! terminating in a header 42 with which the tubes of one of the' exoh angers' 39 communicate at one end The svera banks' of tubes are connected "in series by headers--43 and n The last bank is connected to header 43 from which a' duct 44 extends 'to'the burner side of the 'chamber' As shown-in Figure 3', this duct'communicates with the-lowermost of theseveral' passes Iormed in'the* space within division wall IT by' the bafiles 2l.' The aifromi the recuperato-r thus flows bacl and forth through the division wall absorbing additional heart therefro m, The air is thus in efi'ect, super heated and the wall is cooled simultaneous-ly. Finally', the super-heated air fiows out of` the uppermost pass in the' wall IT, through downcomer 21 and thence into the burnersl fl.

' 'I'he operation of my improved soaking pit .and the` methodof heating ingots which I am thereby enabled to carry out require no further explanatienthan' as already been given in describing ;acterized -by numerous advantages over prior soaking pits and lugat-heating practices. In the first place, local ,overheating and excessive oxidation offthe 'ingots. as a result of impingence of flame thereon' are avoided. In the second place,

' sincethefcombustion of fuel occurs in a confined already been mentioned;

" The combustio n of fu'el ini'the chamber ll is easily controllable. not only to assure the'highe est desirahlertemperature for efficient 'combustion but also a substantial'ly neutral atmosphere of the combustion products in the pit, instead of, one having oxidizing c-haracteris'tics; .y A balanced draft maylreadily :be maintained in the *pit by'a suitable control, of the gases fio wing outwardly through the exhaust duet 33. By this control, the pit is atall times maintained 'full of gas at uniform temperature and pressure, except when.. the cover is removed; Atsuch times, fuel and. air input to the pit should `he reduoed or discontinued. Thestack 'draft may be controlled by asuitable damper or; byvarying the speed of the fan 3'|. Similarly, the fuel-air rai-,io may be controlled-by a damper in the air-supply lineor by controlling the speed of fan 40.'

AlthoughI have illustrated and described but a preferred embodiment andpractice'of theinvention, it willbe recognized that changes in the constructon *and procedure disclosed may be madewithout departing from the spirit'of the invention or the scope of the. appendecl laims.` wlclaimt" i i `1.' An ingot-heating furnace comprising a pit open at the top, having a bottom 'and-side walls.` a. hot-gas' supply fiue for'med in said side walls extending' around the pit at a level adjacent the top of the side walls, inlet passages spacedaround thepit branching from 'said flue and extending throughthe side wall s adjaoent the top thereof, an exhaut flue formed' insaid side walls extnding around the pit at a level adjacent said bottom, *oitlet ;passagesspaced around the pit and extendingfrom the interior thereof to said exhaust flue,-a' colnbustion chamber adj acent said pit and-a passage connecting said chamber to said hot-gas supply flu. I

2`.`Theapparatus defincd by claim 1 characterized by said walls having a ledge adjacent the top thereoi, said inlet passages terminatng in ports openingupwardly through said ledge. y

3. The apparatus defined' by claim 1 characterized by saidombuston chamber being constructecl as an extension on'one side of the pit and solid therewith, said chamber having therein a central partitiori defining forth andfireturn passes of a length and height at least' equal to those of the pit.

4. An ingot-heating furnace comprising a pit open at the top, having a bottom and side walls, a combustion chamber constructed as an extension of the masonry mass of the furnace at one side thereof and solid therewith, said chamber having a central partition wall parallel to one of said 'side walls, defining forth and return passes of a length and height at least equal to' those of the pit, a hot-gas supply flue extending around the pit and communicating therewith,

and a passage connecting said return pass to said flue.

5. The apparatus defined by claim 4 characterized by said partition having air passages therein and said chamber having a burner, and

means conducting air from said last-mentioned passages to said. burner.

u JOHN F; MOWAT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Date Number Name Re. 16,826 Stein Dec. 20, 1927 555,'731 Nesmith Mar. 3, 1896 %3,511 Schmidt et al Nov. 10, 1908 1,711,273 Manker Apr. 30, 1929 1396310 Merkt Feb. 7, 1933 2,029,176 Lindberg Jan. 28, 1936 2,029,580 a Merkt Feb. 4, 1936 2,27'7,592 Keener et al. Mar. 24, 1942 i FOREIGN PATENTS Number Country Date 119,495 Great Britain sept. 26, 1918 

